/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * drivers/watchdog.c
 *
 *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <semaphore.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <tinyara/fs/fs.h>
#include <tinyara/irq.h>
#include <tinyara/kmalloc.h>
#include <tinyara/watchdog.h>

#ifdef CONFIG_WATCHDOG

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/
/* Debug ********************************************************************/
/* Non-standard debug that may be enabled just for testing the watchdog driver */

#ifdef CONFIG_DEBUG_WATCHDOG
#define wddbg    dbg
#define wdvdbg   vdbg
#define wdlldbg  lldbg
#define wdllvdbg llvdbg
#else
#define wddbg(x...)
#define wdvdbg(x...)
#define wdlldbg(x...)
#define wdllvdbg(x...)
#endif

/****************************************************************************
 * Private Type Definitions
 ****************************************************************************/

/* This structure describes the state of the upper half driver */

struct watchdog_upperhalf_s {
	uint8_t crefs;				/* The number of times the device has been opened */
	sem_t exclsem;				/* Supports mutual exclusion */
	FAR char *path;				/* Registration path */

	/* The contained lower-half driver */

	FAR struct watchdog_lowerhalf_s *lower;
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static int wdog_open(FAR struct file *filep);
static int wdog_close(FAR struct file *filep);
static ssize_t wdog_read(FAR struct file *filep, FAR char *buffer, size_t buflen);
static ssize_t wdog_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
static int wdog_ioctl(FAR struct file *filep, int cmd, unsigned long arg);

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const struct file_operations g_wdogops = {
	wdog_open,					/* open */
	wdog_close,					/* close */
	wdog_read,					/* read */
	wdog_write,					/* write */
	0,							/* seek */
	wdog_ioctl					/* ioctl */
#ifndef CONFIG_DISABLE_POLL
	, 0						/* poll */
#endif
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/************************************************************************************
 * Name: wdog_open
 *
 * Description:
 *   This function is called whenever the watchdog timer device is opened.
 *
 ************************************************************************************/

static int wdog_open(FAR struct file *filep)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct watchdog_upperhalf_s *upper = inode->i_private;
	uint8_t tmp;
	int ret;

	wdvdbg("crefs: %d\n", upper->crefs);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		ret = -get_errno();
		goto errout;
	}

	/* Increment the count of references to the device.  If this the first
	 * time that the driver has been opened for this device, then initialize
	 * the device.
	 */

	tmp = upper->crefs + 1;
	if (tmp == 0) {
		/* More than 255 opens; uint8_t overflows to zero */

		ret = -EMFILE;
		goto errout_with_sem;
	}

	/* Save the new open count */

	upper->crefs = tmp;
	ret = OK;

errout_with_sem:
	sem_post(&upper->exclsem);

errout:
	return ret;
}

/************************************************************************************
 * Name: wdog_close
 *
 * Description:
 *   This function is called when the watchdog timer device is closed.
 *
 ************************************************************************************/

static int wdog_close(FAR struct file *filep)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct watchdog_upperhalf_s *upper = inode->i_private;
	int ret;

	wdvdbg("crefs: %d\n", upper->crefs);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		ret = -get_errno();
		goto errout;
	}

	/* Decrement the references to the driver.  If the reference count will
	 * decrement to 0, then uninitialize the driver.
	 */

	if (upper->crefs > 0) {
		upper->crefs--;
	}

	sem_post(&upper->exclsem);
	ret = OK;

errout:
	return ret;
}

/************************************************************************************
 * Name: wdog_read
 *
 * Description:
 *   A dummy read method.  This is provided only to satisfy the VFS layer.
 *
 ************************************************************************************/

static ssize_t wdog_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
{
	/* Return zero -- usually meaning end-of-file */

	return 0;
}

/************************************************************************************
 * Name: wdog_write
 *
 * Description:
 *   A dummy write method.  This is provided only to satisfy the VFS layer.
 *
 ************************************************************************************/

static ssize_t wdog_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
{
	return 0;
}

/************************************************************************************
 * Name: wdog_ioctl
 *
 * Description:
 *   The standard ioctl method.  This is where ALL of the watchdog timer work is
 *   done.
 *
 ************************************************************************************/

static int wdog_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
	FAR struct inode *inode = filep->f_inode;
	FAR struct watchdog_upperhalf_s *upper = inode->i_private;
	FAR struct watchdog_lowerhalf_s *lower = upper->lower;
	int ret;

	wdvdbg("cmd: %d arg: %ld\n", cmd, arg);
	DEBUGASSERT(upper && lower);

	/* Get exclusive access to the device structures */

	ret = sem_wait(&upper->exclsem);
	if (ret < 0) {
		return ret;
	}

	/* Handle built-in ioctl commands */

	switch (cmd) {
	/* cmd:         WDIOC_START
	 * Description: Start the watchdog timer
	 * Argument:    Ignored
	 */

	case WDIOC_START: {
		/* Start the watchdog timer, resetting the time to the current timeout */

		DEBUGASSERT(lower->ops->start);	/* Required */
		ret = lower->ops->start(lower);
	}
	break;

	/* cmd:         WDIOC_STOP
	 * Description: Stop the watchdog timer
	 * Argument:    Ignored
	 */

	case WDIOC_STOP: {
		/* Stop the watchdog timer */

		DEBUGASSERT(lower->ops->stop);	/* Required */
		ret = lower->ops->stop(lower);
	}
	break;

	/* cmd:         WDIOC_GETSTATUS
	 * Description: Get the status of the watchdog timer.
	 * Argument:    A writeable pointer to struct watchdog_status_s.
	 */

	case WDIOC_GETSTATUS: {
		FAR struct watchdog_status_s *status;

		/* Get the current watchdog timer status */

		if (lower->ops->getstatus) {	/* Optional */
			status = (FAR struct watchdog_status_s *)((uintptr_t)arg);
			if (status) {
				ret = lower->ops->getstatus(lower, status);
			} else {
				ret = -EINVAL;
			}
		} else {
			ret = -ENOSYS;
		}
	}
	break;

	/* cmd:         WDIOC_SETTIMEOUT
	 * Description: Reset the watchdog timeout to this value
	 * Argument:    A 32-bit timeout value in milliseconds.
	 */

	case WDIOC_SETTIMEOUT: {
		/* Set a new timeout value (and reset the watchdog timer) */

		if (lower->ops->settimeout) {	/* Optional */
			ret = lower->ops->settimeout(lower, (uint32_t)arg);
		} else {
			ret = -ENOSYS;
		}
	}
	break;

	/* cmd:         WDIOC_CAPTURE
	 * Description: Do not reset.  Instead, called this handler.
	 * Argument:    A pointer to struct watchdog_capture_s.
	 */

	case WDIOC_CAPTURE: {
		FAR struct watchdog_capture_s *capture;

		/* Don't reset on watchdog timer timeout; instead, call this user
		 * provider timeout handler.  NOTE:  Providing handler==NULL will
		 * restore the reset behavior.
		 */

		if (lower->ops->capture) {	/* Optional */
			capture = (FAR struct watchdog_capture_s *)((uintptr_t)arg);
			if (capture) {
				capture->oldhandler = lower->ops->capture(lower, capture->newhandler);
				ret = OK;
			} else {
				ret = -EINVAL;
			}
		} else {
			ret = -ENOSYS;
		}
	}
	break;

	/* cmd:         WDIOC_KEEPALIVE
	 * Description: Reset the watchdog timer ("ping", "pet the dog")
	 * Argument:    Argument: Ignored
	 */

	case WDIOC_KEEPALIVE: {
		/* Reset the watchdog timer to the current timeout value, prevent any
		 * imminent watchdog timeouts.  This is sometimes referred as
		 * "pinging" the watchdog timer or "petting the dog".
		 */

		if (lower->ops->keepalive) {	/* Optional */
			ret = lower->ops->keepalive(lower);
		} else {
			ret = -ENOSYS;
		}
	}
	break;

	/* Any unrecognized IOCTL commands might be platform-specific ioctl commands */

	default: {
		wdvdbg("Forwarding unrecognized cmd: %d arg: %ld\n", cmd, arg);

		/* An ioctl commands that are not recognized by the "upper-half"
		 * driver are forwarded to the lower half driver through this
		 * method.
		 */

		if (lower->ops->ioctl) {	/* Optional */
			ret = lower->ops->ioctl(lower, cmd, arg);
		} else {
			ret = -ENOSYS;
		}
	}
	break;
	}

	sem_post(&upper->exclsem);
	return ret;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: watchdog_register
 *
 * Description:
 *   This function binds an instance of a "lower half" watchdog driver with the
 *   "upper half" watchdog device and registers that device so that can be used
 *   by application code.
 *
 *   When this function is called, the "lower half" driver should be in the
 *   disabled state (as if the stop() method had already been called).
 *
 * Input parameters:
 *   dev path - The full path to the driver to be registers in the TinyAra
 *     pseudo-filesystem.  The recommended convention is to name all watchdog
 *     drivers as "/dev/watchdog0", "/dev/watchdog1", etc.  where the driver
 *     path differs only in the "minor" number at the end of the device name.
 *   lower - A pointer to an instance of lower half watchdog driver.  This
 *     instance is bound to the watchdog driver and must persists as long as
 *     the driver persists.
 *
 * Returned Value:
 *   On success, a non-NULL handle is returned to the caller.  In the event
 *   of any failure, a NULL value is returned.
 *
 ****************************************************************************/

FAR void *watchdog_register(FAR const char *path, FAR struct watchdog_lowerhalf_s *lower)
{
	FAR struct watchdog_upperhalf_s *upper;
	int ret;

	DEBUGASSERT(path && lower);
	wdvdbg("Entry: path=%s\n", path);

	/* Allocate the upper-half data structure */

	upper = (FAR struct watchdog_upperhalf_s *)
			kmm_zalloc(sizeof(struct watchdog_upperhalf_s));
	if (!upper) {
		wddbg("Upper half allocation failed\n");
		goto errout;
	}

	/* Initialize the watchdog timer device structure (it was already zeroed
	 * by kmm_zalloc()).
	 */

	sem_init(&upper->exclsem, 0, 1);
	upper->lower = lower;

	/* Copy the registration path */

	upper->path = strdup(path);
	if (!upper->path) {
		wddbg("Path allocation failed\n");
		goto errout_with_upper;
	}

	/* Register the watchdog timer device */

	ret = register_driver(path, &g_wdogops, 0666, upper);
	if (ret < 0) {
		wddbg("register_driver failed: %d\n", ret);
		goto errout_with_path;
	}

	return (FAR void *)upper;

errout_with_path:
	kmm_free(upper->path);

errout_with_upper:
	sem_destroy(&upper->exclsem);
	kmm_free(upper);

errout:
	return NULL;
}

/****************************************************************************
 * Name: watchdog_unregister
 *
 * Description:
 *   This function can be called to disable and unregister the watchdog
 *   device driver.
 *
 * Input parameters:
 *   handle - This is the handle that was returned by watchdog_register()
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void watchdog_unregister(FAR void *handle)
{
	FAR struct watchdog_upperhalf_s *upper;
	FAR struct watchdog_lowerhalf_s *lower;

	/* Recover the pointer to the upper-half driver state */

	upper = (FAR struct watchdog_upperhalf_s *)handle;
	lower = upper->lower;
	DEBUGASSERT(upper && lower);

	wdvdbg("Unregistering: %s\n", upper->path);

	/* Disable the watchdog timer */

	DEBUGASSERT(lower->ops->stop);	/* Required */
	(void)lower->ops->stop(lower);

	/* Unregister the watchdog timer device */

	(void)unregister_driver(upper->path);

	/* Then free all of the driver resources */

	kmm_free(upper->path);
	sem_destroy(&upper->exclsem);
	kmm_free(upper);
}

#endif							/* CONFIG_WATCHDOG */
